Berakdar, J.

The helicity dependence of the two-electron photoemission from isotropic targets is analysed. As prototype reactions, we consider the double ionization of H^-(¹S^e), He(¹S^e) Li⁺(¹S^e), Be²+(¹S^e) and B³+(¹S^e) upon the absorption of a circularly polarized photon. Assuming the Coulomb field of the nucleus to be dominant over other involved interactions, we derive analytical expressions for the cross sections and their dependence on the photon helicity, i.e. for the circular dichroism in these cross sections. This analysis indicates that the cross sections and the circular dichroism are in uenced in a markedly different manner by the interelectronic correlation. With increasing strength of the Coulomb nuclear field the cross section rapidly diminishes whilst the dichroism remains finite and its sign varies considerably with the nuclear charge. It is analytically concluded that the absence of the dichroism at certain 'non-geometrical' points as well as at certain intermediate excess energies is a direct manifestation of the interelectronic correlation. At threshold and in the high-energy limit negligible dichroism is anticipated.

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